The electromotive force `(emf)` of a galvanic cell is defined as the potential differnece between the elctrodes of the cell when the cell is in

Options

A. its standant state
B. the open circuit
C. the closed circuit
D. its nonstandard state

Answer

B

Explanation

In the normal operation of a galvanic cell, the potential difference (Voltage) across the electrodes is less than the macimum possible voltage of the cell. One reason for this is that it takes energy or work to drive a current through the cell itself. The decrease in cell voltage as current is drawn reflects this energy expenditure within the cell, and the freater the current, the lower the voltage.
Thus, the cell voltage has it maximum value onlu when no current flows. The situation is analogous to measuring the difference between the pressure of water in a faucet and that of the outside atmosphere. We expect this difference to be h ifher if we measure it by a device that does not require us to run water form the faucet. When we do run water, the pressure difference drops.
The maximum possible potential difference between the electrodes of a galvanic cell when no current is drawn out is reffered to as the electromotive force `(emf)` of the cell, or `E_("cell")`. It can be measured by an electronic digital volmeter, which draws hegligible current.
We can also determine which electrode of a cell is the anode and which the cathode from this measurement because the digital voltmeter gives the reading with a sign attached, from which we can deduce the sign, or polarity, of each electrode. The anode of a voltaic cell has nefatice polarity while the cathode has positive polarity.